1. Field of the Invention
This invention relates to a cooling fan for an engine or the like, more particularly to a cooling fan having a metal spacer of a ring shape, a plastic boss of substantially a cylindrical shape that is molded integrally with the spacer as an insert and a plurality of blades that extends outwardly from the boss.
2. Description of the Related Art
A conventional cooling fan has a resin molded portion that is composed of a metal spacer of a ring shape, a plastic boss of substantially a cylindrical shape that is molded integrally with the spacer as an insert and a plurality of blades that extends outwardly from the boss. The conventional cooling fan has no drawn part on an outer periphery of the spacer, so that the spacer lacks in rigidity. Consequently, the conventional cooling fan is deficient in durability and cannot be put into practical use.
In view of the above problem, a part of the spacer was deep-drawn that was inserted into the cylindrical boss of the resin molded portion so as to assure the rigidity of the spacer. Then, sufficient durability was obtained. Moreover, ribs were formed on an inside of the blade of the boss at fixed intervals. Then, strength of the boss improved and the cooling fan had sufficient durability as a whole.
However, where the outer periphery of the spacer is deep-drawn so as to extend up to the boss, an outer diameter of the spacer enlarges thereby to increase production costs. Moreover, where the ribs are provided on the inside of the blade of the boss at constant intervals, the strength may be deficient or an excessive reinforced structure may be obtained depending on the number or shape of the ribs thereby to increase the production costs, too.
An object of the present invention is to provide a cooling fan that is capable of improving durability while limiting a size of an outer periphery of a spacer, a thickness, a size and an arrangement of ribs at an inside of a boss and a thickness of the boss to necessary dimensions thereby to minimize production costs.
According to a first aspect of the invention, there is provided a cooling fan comprising a spacer of a ring shape made of a metal; a boss of substantially a cylindrical shape made of a synthetic resin that is molded integrally with the spacer as an insert; and plural blades that extend outwardly from the boss. The spacer has a deep-drawn part provided on an outer circumferential part thereof at an inside of the boss according to a mounting position of the blade.
According to a second aspect of the invention, there is provided a cooling fan comprising a spacer of a ring shape made of a metal; a boss of substantially a cylindrical shape made of a synthetic resin that is molded integrally with the spacer as an insert; and plural blades that extend outwardly from the boss. The boss has a larger thickness in part at a front edge side of the blade according to a mounting position of the blade.
According to a third aspect of the invention, there is provided a cooling fan comprising a spacer of a ring shape made of a metal; a boss of substantially a cylindrical shape made of a synthetic resin that is molded integrally with the spacer as an insert; plural blades that extend outwardly from the boss; and plural ribs provided on an inner periphery of the boss at intervals in a circumferential direction of the inner periphery of the boss. One or more of the ribs located at around a front edge side of the blade are thicker than other ribs according to a mounting position of the blade.
According to a fourth aspect of the invention, there is provided a cooling fan comprising a spacer of a ring shape made of a metal; a boss of substantially a cylindrical shape made of a synthetic resin that is molded integrally with the spacer as an insert; plural blades that extend outwardly from the boss; and plural ribs provided on an inner periphery of the boss at intervals in a circumferential direction of the inner periphery of the boss. The ribs change heights according to a mounting position of the blade at an outer periphery of the boss.
According to a fifth aspect of the invention, there is provided a cooling fan comprising a spacer of a ring shape made of a metal; a boss of substantially a cylindrical shape made of a synthetic resin that is molded integrally with the spacer as an insert; plural blades that extend outwardly from the boss; and plural ribs provided on an inner periphery of the boss at intervals in a circumferential direction of the inner periphery of the boss. The interval between the ribs at a front edge side of the blade is narrower than the interval between the ribs at a side away from the front edge side of the blade according to a mounting position of the blade.
According to a sixth aspect of the invention, there is provided a cooling fan comprising a spacer of a ring shape made of a metal; a boss of substantially a cylindrical shape made of a synthetic resin that is molded integrally with the spacer as an insert; plural blades that extend outwardly from the boss; and plural ribs provided on an inner periphery of the boss at intervals in a circumferential direction of the inner periphery of the boss. The cooling fan further comprises two or more of following features: the spacer having a deep-drawn part provided on an outer circumferential part thereof at an inside of the boss, the boss having a larger thickness in part at a front edge side of the blade according to a mounting position of the blade, one or more of the ribs located at around a front edge side of the blade being thicker than other ribs according to a mounting position of the blade, the ribs changing heights according to a mounting position of the blade at an outer periphery of the boss and the interval between the ribs at a front edge side of the blade being narrower than the interval between the ribs at a side away from the front edge side of the blade according to a mounting position of the blade.
Further objects and advantages of the invention will be apparent from the following description, reference being had to the accompanying drawings, wherein preferred embodiments of the invention are clearly shown.